From the pic's I can tell the you have purchased a H18 w/ the Black Anodized crossbeams ... EPOv1 Rudder blades ... and early/mid production Magnum Wings. Please look at the serial number etched on the transom as the last three numbers tell you the month and year of production and the last letter tells you the month also ... I believe of when it was assembled/sold/shipped to the dealer. So sometimes the number for the month and the letter are slightly off. RedLine/Red Foam boat production started w/ "684" ... maybe as early as "484" to into 1986 sometime, when Hobie stopped using the red neoprene glue/foam to assemble the boats

Treasure the EPOv1 Rudder Blades ... the replacement EPOv2's are very expensive ... like $400.00 approximently/blade. Never use a "plastic" rudder blade on a H18 as they are too flexible !!! and not up to the loads placed on them.

And the sail pattern you have is called ... "Blue Hawaii's" ... the prettiest sails ever made !!!!

Do you have beach wheels??? w/ cradles ??? cradles are important for a H18, both on the trailer and beach wheels. Look for the thread "H18: the Big Project" ... the best cradles ever!!!!

Shroud "Anchor Bolts" are a particular problematic item ... replace every several years as they fail w/ no notice ... except for a "LOUD BANG" ... and the mast comes down .... ruining your day !!!

Pay particular attention to posts from Mr Matt Bounds, Mr Steven Cooley, Mr Jim Sohn and Mr SRM .... they have many many years ... decades of experience on Hobie Cats ...

So review our past posts ... there is a lot of information available for the H18 here on this forum ... it will keep you busy .... any questions ... just ask ... the only "stupid" question is the one you don't ask ... remember we all started out as "newbies" to the H18 at some point in time ... (for some of us we just don't want to admit to how long ago that was ...)

Judging by your "inside the hull" picture, I would add a few layers of glass/epoxy to that area. From 2-3" outside of the first bolt to 2-3" outside the last bolt and down 6-8", on the inboard and out board sides of each hull. Also remove the excess glue in that area to produce a nice radius and glass the hull to deck joint as well. Since you're running wings I would do the same the same at the aft beam saddle as well, and add anchor plates there too.